The present invention relates to an electrohydraulic servovalve. Generally, a servovalve belongs to the class of apparatus transforming an electric magnitude, current or voltage, into a corresponding hydraulic magnitude, i.e. a pressure or a flowrate.
Servovalves are used principally as interface elements between an electric control and a mechanical action in electrohydraulic control systems which for several years have known an increasing development. The applications thereof are not then limited to the aeronautics or armaments fields but have penetrated other fields and electrohydraulic servosystems can be found on machine tools, in metallurgy, on mobile equipment and on machines for transforming plastic materials, among others.
The servovalve, from the raw energy supplied by a hydraulic generator, restores to a power member, motor or cylinder and piston device, a part thereof in ordered form. The ratio between the electric control power and the controlled hydraulic power is currently between 10.sup.4 and 10.sup.6. In fact, with an electric signal of a few hundredths or tenths of a watt an oil flowrate of several tens, even several hundreds of kilowatts may be controlled.
For correct operation of an open or closed servocontrol loop, comprising a servovalve, it is usually desirable for the characteristic response of the servovalve to be as linear as possible. At the same time, as for any other component, attempts are made to increase the performances thereof, speed of response, output power, control fineness about the zero point etc., while reducing the charges such as energy losses, space occupancy and cost price.
Up to the present time, the linearity and the other qualities are provided by using manufacturing techniques of very high quality, even close to the presently obtainable limits. This results in high costs.
The aim of the present invention is to ensure the desired ratio between the control signal and the action which results therefrom, by using means which do not necessarily involve said very high precision manufacturing techniques.